The present invention relates to a supporting structure for supporting an air filter, capable of suppressing as much as possible the transmission of vibration from, for example, an automobile engine to an air filter attached to the engine.
Conventionally, the air filter is attached to a bracket fixed to the engine and also to a carburetor, directly or indirectly through a vibration damping member made of a resilient material such as rubber. If the resilient vibration damping member is used for supporting the casing of the air filter, the transmission of vibration from the engine to the casing is considerably suppressed thanks to the vibration damping effect of the vibration damping member. However, the vibration of the engine body is directly transmitted to the cap of the air filter through a center bolt for centering and fixing the cap. Thus, the cap and the casing of the air filter constitute different vibration systems. If the air filter is mounted solely through a medium of a gasket without the resilient vibration damping member, the vibration is directly transmitted to the air filter from the engine body.
As is well known, the automobile engine is a vibration source which produces vibrations of considerably large amplitudes. The vibration of the engine body, when transmitted to members formed of thin-walled iron plates such as air filter, causes a vibration of these members to produce unfavourable noises. The air filter may be composed of iron plates having greater thicknesses, in order to withstand the vibration transmitted from the engine. In such a case, however, the weight of the air filter as a whole is increased impractically.
It is also possible to interpose, as stated before, a resilient vibration damping member between the casing of the air cleaner and the engine. This, however, cannot overcome the problem of vibration of the air cleaner cap, because the vibration is transmitted to the air filter cap directly from the engine through the center bolt. Thus, noise is inevitably generated by the air filter cap, and, since the cap and the casing of the air cleaner constitute different vibration systems, the cap and the casing are vibrated at different amplitudes and frequencies, adversely affecting the juncture between the cap and the casing, as well as the internal air filtration elements. The vibration suppressing effect on the casing of the air filter, provided by the resilient vibration member made of rubber or the like, will be reduced almost to a half unless an effective measure is taken for suppressing the transmission of vibration to the cap of the air filter.